Core drill latch

ABSTRACT

A core barrel inner tube assembly, having a latching mechanism which can latch the assembly into the drill string to prevent upward movement of the assembly relative to the string as it is lowered down a drill hole and which can be released by the application of drilling fluid pressure to allow normal operation during drilling.

United States Patent 1 91 Koepke CORE DRILL LATCH [75] Inventor: HorstKoepke, East Coburg, Australia [73] Assignee: Mindrill Limited, Preston,Victoria,

Australia 221 Filed: Dec. 6, 1968 21 Appl. No.: 781,743

Foreign Application Priority Data Dec. 6, 1967 Australia ..30,828/67 US.Cl ..175/247 Int. Cl ..E2lb 9/20, E21b 25/00 Fieldjof Search.......175/237-239, 244,

1 51 Apr. 3, 1973 Primary ExaminerDavid H. Brown Attorney-Woodhams,Blanchard and Flynn [57] ABSTRACT A core barrel inner tube assembly,having a latching mechanism which can latch the assembly into the drillstring to prevent upward movement of the assembly relative to the stringas it is lowered down a drill hole and which can be released by theapplication of drilling fluid pressure to allow normal operation duringdrilling.

6 Claims, 5 Drawing Figures V) 43 &j%

77 7 Z 2 42 J I i CORE DRILL LATCH BACKGROUND OF THE INVENTION In coredrilling, a tubular drill string having an annular drill bit is employedand the core produced by the bit is received by an inner tube located inthe outer or drill string tube and this inner tube and its associatedmounting is known as a core barrel inner tube assembly.

It is desirable in order to avoid damage to the core that the inner orcore receiving tube be mounted in the drill string in such a way that itcan remain stationary while the drill string rotates during drilling andthat means be provided to signify when the core barrel is full or whenit jams in any way during drilling. This can be achieved by suspendingthe core receiving tube from a spindle by means of a bearing andmounting the spindle and the inner tube within the outer casing foraxial movement therein against spring loading on the spindle, thearrangement being such that when the core barrel is filled or if it jamsduring drilling, the inner tube and spindle assembly rises against thespring pressure and cuts off or restricts supply of drilling fluid tothe bit through ports in the spindle thereby to cause a rise in pressurein the drilling fluid circuit which serves as a warning signal to theoperator.

A core lifter is disposed at the bottom end of the the bottom whendrilling is completed. In one type of core barrel, the core lifter maynormally be disposed around the lower end of the inner tube so that itdoes not interfere with the core passing into the tube during drillingand is only' exposed to the core when the inner tube and spindle areraised. One particular core barrel incorporating all of the featuresoutlined above is fully described in our prior Australian PatentApplication No. 11787/66, the core lifter in that case being in the formof a split frusto-conical ring which is closed by engagement with atapered seat in the outer drill tube when the whole drill string islifted after a drilling operation.

It has been found that the whole purpose of having a core lifter of thetype which is normally shielded by the inner tube is often defeated bythe fact that conditions frequently arise which cause the core lifter tobe exposed prematurely. One such set of conditions occurs when thebarrel is being lowered or dropped down a drill hole and the upwardforces caused by water in the hole act in the same manner as the upwardforces on a full length core to cause the inner tube to retract andexpose the core lifter. The present invention enables prevention of thisoccurrence by quite simple modifications to the barrel.

SUMMARY According to the invention there is provided a core barrel innertube assembly having latching means thereon to latch said assembly intoa drill string to prevent upward movement of the assembly relative tothe drill string, said latching means being releasable by application offluid pressure.

The inner tube assembly according to this invention may thus be latchedinto the drill string to prevent upward movement of the assemblyrelative to the string as it is lowered into a drill hole. When thestring is positioned in the hole and drilling fluid is applied, theassembly is unlatched and is free to rise in the string under theinfluence of upward forces in the normal way.

Preferably, the latching means: comprises a hollow spindle, latchingelements mounted on the spindle and movable between a latching positionand a nonlatching position, and a piston slidable within the spindlebetween a first position in which it locks the latching elements in thelatching position and a second position in which said latching elementsare freed to move to the non-latching position, movement of the pistonfrom the first position to the second position being brought about bythe application of the fluid pressure.

In order that the invention may be more fully explained one particularembodiment thereof will now be described in detail with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS:

In the drawing FIG. 1 is a vertical section through part of a corebarrel having a spindle modified in accordance with the presentinvention and shows a piston within the spindle in a raised position;

FIG. 2 is a cross-section on the line 22 in FIG. 1;

FIG. 3 is a cross-section on the line 3-3 in FIG. 1;

FIG. 4 is a vertical section similar to FIG. 1 but shows the pistonwithin the spindle in a lower position; and

FIG. 5 is a cross-section on the line 55 inFIG. 4.

The drawing shows part only of the upper end of a non-wire-line typecore barrel inner tube assembly. As is normal, the spindle 11 isslidable within the outer casing 12 of the core barrel. Spindle 11comprises upper and lower members 13, 14 which are connected by screwthreads at 16 and locked together by an internally threaded lockingring". The outer casing 12 comprises upper and lower tubes 18, 19screwed to one another at 21. Spindle l 1 is biased against upwardmovement relative to outer casing 12 by a helical compression springacting between the upper end of the casing and the upper end of thespindle (not shown). The lower end of spindle 1 1 has an internallythreaded spigot 22 on which a hanger bearing 23 is mounted and retainedby a retaining pin 24 which screws into the spigot. Hearing 23 supportsa core lbarrel inner tube as sembly 26. Inner tube assembly 26 is ofconventional construction and only its upper end is shown in thedrawing. Its lower end comprises the inner core receiving tube of thebarrel.

Spindle 11 has a central bore 27 which receives a piston 28 with a tightsliding fit. Piston 28 has a tubular upper end enclosing a central bore29 and has a solid bottom end 31. A little above the solid bottom end 31of piston 28, a cross pin 32 extends diametrically through its tubularpart to engage at its ends a pair of longitudinal slots 33 machined inthe spindle to permit sliding movement of the cross pin therein whenpiston 28 is raised and lowered with respect to the spindle.

A hole 34 is drilled diametrically through spindle 11 and receives apair of steel latch balls 36, the outer end of hole 34 being reduced indiameter, for example, by peening, to prevent the balls passing outfully through these ends. The upper end of piston 28 has a pair ofcircular recesses 37 formed at diametrically opposite locations at itsouter periphery and the lower solid end 31 of the piston has a bore 38drilled through it to receive a pair of detent balls 39 which are biasedoutwardly by a helical compression spring 41.

When piston 28 is in its raised position shown in FIG. 1, detent balls39 are forced outwardly by spring 41 into engagement with a pair ofholes 42 in the wall of spindle 11 to provide a detent action whichholds the piston in this position. When the piston is held in thisraised position, the whole spindle and piston assembly is prevented frommoving upwardly with respect to the outer casing by contact of latchballs 36 with an outwardly and downwardly sloping frusto-conicalshoulder 43 on outer casing 12. Shoulder 43 is formed by the lower endof the upper tubular member 18 of the outer casing. Thus the spindle andinner core receiving tube cannot rise within the outer casing whenpiston 28 is held in its upper position.

Before the drill string is lowered into the hole the piston 28 is movedto its upper position and the core barrel inner tube assembly ispositioned on the drill string. The drill string is then lowered intothe hole and with the piston thus held in its'upper position by thedetent balls 39. The core barrel assembly is prevented by the engagementbetween the latch balls 36 and the shoulder 43 from moving upward underpressure from fluid in the hole. On arrival at the bottom of the hole,water under pressure is pumped down the drill string into the interiorof spindle 11 and acts on piston 28 so as to overcome the detent actionof balls 39 and move the piston downwardly relative to the spindle tothe position shown in FIG. 2. This allows the latch balls 36 to fallback into recesses 34 and so enables the spindle and inner tube assemblyto rise in normal fashion when the core receiving tube is full orbecomes jammed. The movement of piston 28 relative to spindle 11 alsobrings a pair of openings 44 in the piston into line with holes 42 inthe spindle thus allowing drilling fluid to pass to annular passage 46between the upper end of the inner tube assembly 26 and the outer casing12 whence it passes in normal fashion down to the bit. A

V groove 47 is formed in the lower end of piston 28 to through the drillstring from a first position in which it locks the latch element meansin said latching condition to a second position such that the latchingelement means is freedto adopt the non-latching condition.

2. A core drill according to claim 1, wherein the drill string includesa drill tube provided on its inner surface with a downwardly facingabutment adapted to be engaged by said latching element means.

3. In a core drill of the type having a core barrel inner tube assemblywhich must, during drilling, be capable of upward movement within adrill string, comprising the improvement wherein said assembly comprisesa hollow spindle, latching elements mounted in the spindle and movablebetween a latching position and a nonlatching position, and a pistonslidable within the spindle between a first position in which it locksthe latching elements in the latching position and a second position inwhich said latching elements are freed to move to the non-latchingposition, the piston being movable from the first position to the secondposition by the application of drilling fluid down through the drillstring on commencement of a drilling operation.

4. In a core drill according to claim 3, wherein said latching elementsare balls carried in openings in the peripheral wall of the spindle andadapted, when in the latching position, to project outwardly therefrom,and the piston is provided with recesses which, when the piston is inthe second position, are aligned with said openings to allow the ballsto retract into the recesses thereby unlatching the assembly.

5. In a core drill according to claim 4 and further comprising detentmeans adapted to hold the piston in the first position but to bereleased on the said application of the fluid pressure. 7 p

6. In a core drill according to claim 5, wherein said detent meanscomprises spring-loaded balls carried by the piston and adapted toengage in ports provided in the wall of the spindle when the piston isin the first position, and the piston is provided with fluid passageswhich, when the piston is in the second position, are aligned with saidports to provide a passage for drilling fluid through the assembly.

1. In a core drill of the type having a core barrel inner tube assemblywhich must, during drilling, be capable of upward movement within adrill string, the improvement comprising latch element means movablebetween a latching condition for latching the assembly to the drillstring to prevent said upward movement of the assembly and anon-latching condition permitting said upward movement, and a lockingmember movable by the pressure of drilling fluid applied down throughthe drill string from a first position in which it locks the latchelement means in said latching condition to a second position such thatthe latching element means is freed to adopt the non-latching condition.2. A core drill according to claim 1, wherein the drill string includesa drill tube provided on its inner surface with a downwardly facingabutment adapted to be engaged by said latching element means.
 3. In acore drill of the type having a core barrel inner tube assembly whichmust, during drilling, be capable of upward movement within a drillstring, comprising the improvement wherein said assembly comprises ahollow spindle, latching elements mounted in the spindle and movablebetween a latching position and a non-latching position, and a pistonslidable within the spindle between a first position in which it locksthe latching elements in the latching position and a second position inwhich said latching elements are freed to move to the non-latchingposition, the piston being movable from the first position to the secondposition by the application of drilling fluid down through the drillstring on commencement of a drilling operation.
 4. In a core drillaccording to claim 3, wherein said latching elements are balls carriedin oPenings in the peripheral wall of the spindle and adapted, when inthe latching position, to project outwardly therefrom, and the piston isprovided with recesses which, when the piston is in the second position,are aligned with said openings to allow the balls to retract into therecesses thereby unlatching the assembly.
 5. In a core drill accordingto claim 4 and further comprising detent means adapted to hold thepiston in the first position but to be released on the said applicationof the fluid pressure.
 6. In a core drill according to claim 5, whereinsaid detent means comprises spring-loaded balls carried by the pistonand adapted to engage in ports provided in the wall of the spindle whenthe piston is in the first position, and the piston is provided withfluid passages which, when the piston is in the second position, arealigned with said ports to provide a passage for drilling fluid throughthe assembly.